In the 3 hour twilight race he took the lead on the first lap having started in 3rd place. An early puncture dropped him back to 8th but he made his way back to the lead and claimed the overall win of the race. At the 6 Hours of Utah Rydquist claimed the overall pole position and won the class together with team-mates Beau Borders and Mike Holland. In the NASA WERC season finale, the 4 Hours of Sonoma, Rydquist again shared driving duties with Beau Borders. Rydquist started from pole by virtue of having the leading car in the fastest class, handed the car off in the lead to Borders who went on to secure the overall win. The total season points earned Rydquist and the team the 2018 NASA WERC ESR Championship title. The 2018 25 Hours of Thunderhill marked Rydquist's fifth start in this race. Once again he raced with Mike Holland, Beau Borders and Troy Lindstrom in the Prototype Development Group's #4 Factory Five Racing GTM featuring Hankook Tire as title sponsor. The team challenged the Toyo Tires Flying Lizard Porsche 997 RSR piloted by Wolf Henzler, Johannes van Overbeek, Justin Marks, Charlie Hayes, and Andy Wilzoch for ES class pole and intermittently led the class. Ultimately Rydquist and his team scored a best ever finish for the PDG team claiming 2nd in the ES class and 3rd overall behind the Porsche (ES) and One Motorsports Hankook Tire Radical SR3 (ESR). In 2019 Rydquist entered two different sprint racing leagues, the SCCA Trans Am Series presented by Pirelli West Coast Championship, and the United States Touring Car Championship. Rydquist's first Trans Am Series appearance was at Sonoma Raceway. Starting from last on the grid as a result of a schedule conflict with his full season USTCC campaign, Rydquist raced through the field to take a commanding SGT class win and a 4th overall finish in the field of TA, TA2, SGT and GT cars. At Circuit of the Americas all Trans Am championships raced together. Rydquist won the West Coast SGT category and finished 4th overall among the National entries. In the USTCC series Rydquist started off with a grand slam, capturing pole position, setting the fastest lap and winning overall in the season opener at Las Vegas Motor Speedway. He also won from pole position at Sonoma Raceway, Laguna Seca and Thunderhill, claiming the USTCC